The idea for Adi Rule’s new young adult novel, The Hidden Twin, started with an NHPR story she heard about poisonous gardens.

“Right! That’s the face I made! There are these gardens that have plants that are harmful and poisonous, and I thought that would be a really cool — not plot, but setting or something,” Rule said over lunch — French bread pizza and grape soda — at Johny’s Pizza in Hooksett last week. “I wanted the plants to kind of be involved with a murder. Death by garden! It didn’t really come out that way, but plants are a really big part of this book.”

The Northwood author began drafting a little before her first title, Strange Sweet Song, came out in 2014, and she’s since spent long days writing to get the story to her editor on time. She mapped it out on her computer, sometimes at home, sometimes at her parents’ cabin on Donnell Pond in Franklin, Maine, about 40 minutes outside Bar Harbor.

This book, like Song, is fantastical, but also futuristic. It’s about a girl, Redwing, who has spent 18 years living in a small attic room, while her identical sister, Jey, has lived a public life as an only child. Their father had hoped Redwing might grow into a normal person — not the wicked creature mythology promised — which is why he spared her life as an infant. But when she switches places with her sister one day, she’s attacked and forced to unleash her powers and her secret.

The city the twins live in has hissing pipes and curving temples, and it’s located on the side of a volcano. There’s an excess of hot water — ice cubes are a luxury — and birds. Instead of horses, people ride ostriches, and instead of dogs, they have pet raptors.

Rule liked writing this one, she said. The tone was fun, the protagonist confident and sassy.

“It’s a little bit funnier than what I had been working on, so it was a little refreshing for me to get to work on something funny,” Rule said. “It’s also a little bit of a lighter story; it’s about the destruction of the world rather than opera!”

Creating a magical world comes with challenges, but they’re fun challenges, in Rule’s opinion. She got to make up gods, myths and places, and the only research involved was looking up names to ensure her fictitious people, places and things didn’t already exist in the real world. For her, establishing those details and boundaries is key when writing fantasy.

“If you can really kind of imagine how everything fits together, and it makes sense to you, then you don’t have to work as hard,” Rule said.

Rule has a variety of events in New Hampshire this month, starting with a book launch party at MainStreet BookEnds. Bookstore owner Katharine Nevins said via phone she was excited to cater to the next talented Rule generation; she remembers seeing the author coming in as a teeneger along with her mother, New Hampshire writer and storyteller Rebecca Rule.

“I really do think she’s going places,” Nevins said. “I think the writing’s great, and she’s in with a wonderful publishing house. She’s got really fresh great ideas, and she writes for the right genre. She’s nailing it.”

Rule’s next project is a magical realism novel set in Maine tentatively called Shoes. It’s currently on submission, though the first 30 pages will appear in the Hunger Mountain Journal for the Arts this spring. It’s the second novel she ever wrote, the one she initially sent to her agent for query. (Her agent said it needed work, and she’s since revised.)

She’s also written one chapter of a horror novel, inspired by working at the Wentworth-Coolidge Mansion in Portsmouth.

“It has 40-something rooms — though we can’t agree on how many rooms it has. We can’t even agree on how many floors it has. It’s like this crazy Frankenstein house,” Rule said.

Whenever she’s not writing, she’s running a blog for her alma mater, the Vermont College of Fine Arts, where she earned her MFA, or she’s working as a freelancer.